linux-kernel - Re: [PATCH v1 0/5] livepatch: klp-convert tool

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Date: Wed, 10 Apr 2024 12:32:18 -0300
From: Marcos Paulo de Souza <mpdesouza@...e.com>
To: Lukas Hruska <lhruska@...e.cz>
Cc: Petr Mladek <pmladek@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-kbuild@...r.kernel.org,
	Marcos Paulo de Souza <mpdesouza@...e.com>
Subject: Re: [PATCH v1 0/5] livepatch: klp-convert tool - Minimal version

On Mon,  6 Nov 2023 17:25:08 +0100 Lukas Hruska <lhruska@...e.cz> wrote:

> Summary
> -------
> 
> This is a significantly simplified version of the original klp-convert tool.
> The klp-convert code has never got a proper review and also clean ups 
> were not easy. The last version was v7, see 
> https://lore.kernel.org/r/20230306140824.3858543-1-joe.lawrence@redhat.com
> 
> The main change is that the tool does not longer search for the 
> symbols which would need the livepatch specific relocation entry.
> Also klp.symbols file is not longer needed.
> 
> Instead, the needed information is appended to the symbol declaration
> via a new macro KLP_RELOC_SYMBOL(). It creates symbol with all needed
> metadata. For example:
> 
>   extern char *saved_command_line \
>                  KLP_RELOC_SYMBOL(vmlinux, vmlinux, saved_command_line, 0); 
> 
> would create symbol
> 
> $>readelf -r -W <compiled livepatch module>:
> Relocation section '.rela.text' at offset 0x32e60 contains 10 entries:
>     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
> [...]
> 0000000000000068  0000003c00000002 R_X86_64_PC32          0000000000000000 .klp.sym.rela.vmlinux.vmlinux.saved_command_line,0 - 4 
> [...]
> 
> 
> The simplified klp-convert tool just transforms symbols
> created by KLP_RELOC_SYMBOL() to object specific rela sections
> and rela entries which would later be proceed when the livepatch
> or the livepatched object is loaded.
> 
> For example, klp-convert would replace the above symbols with:
> 
> $> readelf -r -W <livepatch_module_proceed_by_klp_convert>
> Relocation section '.klp.rela.vmlinux.text' at offset 0x5cb60 contains 1 entry:
>     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
> 0000000000000068  0000003c00000002 R_X86_64_PC32          0000000000000000 .klp.sym.vmlinux.saved_command_line,0 - 4 
> 
> 
> Note that similar macro was needed also in the original version
> to handle more symbols of the same name (sympos).
> 
> Given the above, add klp-convert tool; integrate klp-convert tool into
> kbuild; add data-structure and macros to enable users to annotate
> livepatch source code; make modpost stage compatible with livepatches;
> update livepatch-sample and update documentation.
> 
> 
> Testing
> -------
> 
> The patchset selftests build and execute on x86_64, s390x, and ppc64le
> for both default config (with added livepatch dependencies) and a larger
> SLE-15-ish config.
> 
> 
> Summary of changes in this minimal version
> ------------------------
> 
> - rebase for v6.5
> - cleaned-up SoB chains (suggested by pmladek)
> - klp-convert: remove the symbol map auto-resolving solution
> - klp-convert: add macro for flagging variables inside a LP src to be resolved by this tool
> - klp-convert: code simplification

Do we have anything that blocks klp-convert-mini to be merged, or something that
needs to be fixed?

Thanks,
  Marcos

> 
> Previous versions
> -----------------
> 
> RFC:
>   https://lore.kernel.org/lkml/cover.1477578530.git.jpoimboe@redhat.com/
> v2:
>   https://lore.kernel.org/lkml/f52d29f7-7d1b-ad3d-050b-a9fa8878faf2@redhat.com/
> v3:
>   https://lore.kernel.org/lkml/20190410155058.9437-1-joe.lawrence@redhat.com/
> v4:
>   https://lore.kernel.org/lkml/20190509143859.9050-1-joe.lawrence@redhat.com/
> v5:
>   (not posted)
>   https://github.com/joe-lawrence/klp-convert-tree/tree/klp-convert-v5-devel
> v6:
>   https://lore.kernel.org/live-patching/20220216163940.228309-1-joe.lawrence@redhat.com/
> v7:
>   https://lore.kernel.org/all/20230306140824.3858543-1-joe.lawrence@redhat.com/